Competitive binding assay for thyroxine using in vitro selected oligonucleotides

Area of Science:

• Biochemistry
• Molecular Biology
• Analytical Chemistry

Background:

• Traditional immunoassays for detecting small molecules like thyroxine (T4) often rely on antibodies.
• Antibody-based assays can face challenges with specificity, particularly when distinguishing between structurally similar molecules such as T4 and liothyronine (T3).
• The development of alternative molecular recognition elements is crucial for advancing diagnostic and analytical techniques.

Purpose of the Study:

• To describe a novel binding assay for thyroxine (T4) utilizing DNA aptamers selected through in vitro methods.
• To demonstrate the ability of these DNA aptamers to selectively bind T4 in the presence of the structurally similar hormone T3.
• To establish a new platform for T4 detection that bypasses the need for traditional antibody-based approaches.

Main Methods:

• In vitro selection (SELEX) was employed to identify oligodeoxyribonucleotides (DNA) with high affinity and specificity for T4.
• Selected DNA aptamers were labeled with biotin or a radioisotope for detection purposes.
• The developed DNA-based assay was validated by measuring T4 concentrations in the presence of varying levels of T3.

Main Results:

• Specific DNA sequences were successfully selected that exhibit selective binding to T4.
• The labeled DNA aptamers enabled the detection of T4.
• The assay demonstrated effective discrimination between T4 and T3, indicating high specificity.
• The assay's performance suggests its potential utility in T4 quantification.

Conclusions:

• Oligodeoxyribonucleotides selected via in vitro methods can serve as effective binding agents for small molecules like T4, replacing antibodies.
• This DNA-based assay offers a promising alternative for the specific detection of T4, even in complex biological samples containing interfering substances like T3.
• The methodology provides a foundation for developing novel, highly specific diagnostic tools for thyroid hormone analysis.